Copper interconnection, method for forming copper interconnection structure, and semiconductor device

ABSTRACT

A copper interconnection structure includes an insulating layer, an interconnection body including copper and a barrier layer surrounding the interconnection body. The barrier layer includes a first barrier layer formed between a first portion of the interconnection body and the insulating layer. The first portion of the interconnection body is part of the interconnection body that faces the insulating layer. The barrier layer also includes a second barrier layer formed on a second portion of the interconnection body. The second portion of the interconnection body is part of the interconnection body not facing the insulating layer. Each of the first and the second barrier layers is formed of an oxide layer including manganese, and each of the first and the second barrier layers has a position where the atomic concentration of manganese is maximized in their thickness direction of the first and the second barrier layers.

This application claims priority under 35 U.S.C. § 119 from Japanesepatent application Serial No. 2008-236211, filed Sep. 16, 2008, entitled“Copper interconnection structure, semiconductor device and method forforming copper interconnection structure”, which is incorporated hereinby reference in its entirety.

TECHNICAL FIELD

The present invention relates to a copper interconnection provided withan interconnection body made of copper on an electric insulating layer,a method for forming the copper interconnection, and a semiconductordevice provided with the copper interconnection as a circuitinterconnection.

BACKGROUND OF THE INVENTION

Copper (Cu) has a lower resistivity (1.7 μΩ·cm) compared to aluminum(Al) with a resistivity of 2.7 μΩ·cm. Additionally, copper has a higherresistance against electro-migration and stress-migration and has beenused as a material for manufacturing an interconnection body insemiconductor devices. Examples of semiconductor devices may includesilicon semiconductor devices including large scale integrated (LSI)systems, flash memory devices or the like, or large size liquid crystaldisplay devices (LCD) (for example, refer to patent documents 1 to 3).

[Patent Document 1]: Japanese Unexamined Patent Application PublicationNo. 2005-277390

[Patent Document 2]: International Publication No. WO2006/025347A1

[Patent Document 3]: International Publication No. WO2007/100125A1

For example, in a silicon LSI system used as a central processing unit(CPU), copper interconnection with damascene structure are used as aninterconnection body. In this structure, copper which composes theinterconnection body, is formed so as to fill the inside of trenches orvia holes provided on an insulating layer made from silicon dioxide(SiO₂) or the like (refer to non-patent document 1).

[Non-Patent Document 1] “Semiconductor Device (2^(nd) edition)—Physicsand Technology” by S. M. Sze (ISBN4-7828-5550-8 C3055), Oct. 5, 2005,Sangyo Tosho, Co., Ltd., third impression of second edition, P355-356.

In order to prevent the degradation of insulating properties of theinsulating layer, due to the atomic diffusion of copper forming theinterconnection body into the insulating layer, or on the other hand, toprevent an increase in the electric resistance of the copperinterconnection body, due to the atomic diffusion of atoms composing theinsulating layer, such as silicon (Si) into the interconnection body, itis common to configure a copper interconnection structure including abarrier layer formed between the insulating layer and the copperinterconnection body. This barrier layer may prevent the mutualdiffusion of atoms while forming the copper interconnection structure(for example, refer to patent documents 4 to 6).

[Patent Document 4] Japanese Unexamined Patent Application PublicationNo. H01-202841

[Patent Document 5] Japanese Unexamined Patent Application PublicationNo. H11-186273

[Patent Document 6] Japanese Unexamined Patent Application PublicationNo. 2001-44156

Conventionally, the barrier layer of the copper interconnectionstructure is made from tungsten nitride (WN) (for example, refer topatent document 7), tantalum (Ta) (for example, refer to patent document8), rhenium (Re) (for example, refer to patent document 9) and the like.

[Patent Publication 7] Japanese Unexamined Patent ApplicationPublication No. 2000-068269

[Patent Document 8] Japanese Unexamined Patent Application PublicationNo. 2004-266178

[Patent Document 6] Japanese Unexamined Patent Application PublicationNo. 2007-096241

In recent years, in view of the necessity for decreasing theinterconnection width (32 nm or less) to increase the LSI integrationdensity, a technique has been disclosed to form a thin barrier layer.The thin barrier layer is formed from a self forming manganese oxidelayer or the like using a copper layer containing an additional elementsuch as manganese (Mn). The additional element of the copper layer has adiffusion coefficient greater than the self diffusion coefficient ofcopper (refer to patent publications 1 to 3 above).

In order to form a barrier layer using a copper layer containingmanganese (Mn), it is common to first deposit a copper alloy layer so asto cover an inner surface of a trench opening provided on an insulatinglayer. Examples of the insulating layer may include porous silicondioxide (SiO₂), silicon carbide oxide (SiOC) or the like. Second, it iscommon to bury copper, which forms the interconnection body, into aremaining space of the trench opening or via hole, and then heattreating the copper alloy layer and the copper interconnection body inan atmosphere containing oxygen molecules.

By this heat treatment, a barrier layer containing silicon (Si), oxygen(O), and manganese (Mn) is formed between the insulating layer and thecopper interconnection body (for example, refer to patent documents 1and 2 above). Alternatively, a barrier layer containing silicon (Si),oxygen (O), manganese (Mn), and copper (Cu) may be formed (refer topatent document 3 above). It is also known that an additional barrierlayer may also be formed in close proximity to a so-called open surfacearea, such as an upper surface of the copper interconnection body, wherethe additional barrier layer is not facing the insulating layer. Theadditional barrier layer is formed by a reaction with the atmospherecontaining oxygen molecules when the heat treatment is applied (forexample, refer to patent documents 1 to 3 above).

In the barrier layer, formed between the copper interconnection body andthe insulating layer, some requirements, such as an atomic concentrationof manganese distribution, has been already known to provide a barrierlayer with sufficient barrier properties (refer to patent document 3above). Meanwhile, it is still unclear what type of internalconfiguration may exercise effective barrier functions for the barrierlayer formed the open surface of the copper interconnection body. Inaddition, it is further unclear what types of process may be used toform a stable barrier layer, on the open surface of the copperinterconnection body, with effective barrier properties.

The present invention is made under the above-mentioned situation. Thepurpose of the present invention is to provide a copper interconnectionstructure having an effective barrier function in the barrier layer onthe open surface of the copper interconnection body by providing anappropriate internal structure in the barrier layer. Further, thepurpose of the present invention is to provide a method for forming thecopper interconnection structure including the barrier layer having suchan effective barrier function. Further, the purpose of the presentinvention is to provide a semiconductor device having the copperinterconnection structure as a circuit interconnection.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention, a copperinterconnection structure includes:

an insulating layer;

an interconnection body including copper; and

a barrier layer surrounding the interconnection body, wherein thebarrier layer includes:

-   -   a first barrier layer formed between a first portion of the        interconnection body and the insulating layer, wherein the first        portion of the interconnection body is a part of the        interconnection body that faces the insulating layer, and        -   a second barrier layer formed on a second portion of the            interconnection body, wherein the second portion of the            interconnection body is a part of the interconnection body            not facing the insulating layer, and wherein:    -   each of the first and the second barrier layers is formed of an        oxide layer including manganese, and    -   each of the first and the second barrier layers has a position        where the atomic concentration of manganese is maximized in        their thickness direction of the first and the second barrier        layers.

In the first aspect of the present invention described above, each ofthe first and second barrier layers is formed of an oxide layerincluding manganese (Mn). Further, each of the first and the secondbarrier layers has a position where the atomic concentration ofmanganese is maximized in their thickness direction of the first and thesecond barrier layers. Therefore, in each of the first and the secondbarrier layers, manganese is surely converted into an oxide layer withelectrical insulating properties. In this way, the barrier layersprevent the atomic diffusion of copper, from the interconnection bodyinto the insulating layer. In addition, the atomic diffusion of atomscomposing the insulating layer, e.g. silicon (Si), into theinterconnection body can surely be prevented. Therefore, it is possibleto produce an interconnection body featuring a barrier layer with ahigher barrier property, against the atomic diffusion, and also superiorin electrical insulating properties. In addition, it is also possible toprovide a copper interconnection structure featuring an interconnectionbody with a lower electrical resistivity and higher conductivity.

In accordance with a second aspect of the present invention, a methodfor forming a copper interconnection structure includes the steps of:

forming an opening in an insulating layer, wherein the opening comprisesan inner surface side facing the insulating layer;

forming a copper alloy layer including manganese having an atomicconcentration of not less than 1.0 atom % and not more than 25 atom % onthe inner surface side;

forming a buried copper over the copper alloy layer so as tosubstantially filling the opening; and

applying a heat treatment under a predetermined condition after theburying step, wherein the predetermined condition includes:

-   -   a temperature of not less than 150° C. and not more than 450°        C., and    -   oxygen partial pressure being adjusted to be less than an atomic        concentration of oxygen (N_(o)) in the copper alloy layer        according to:

N _(o) =N _(Mn) *D _(o) /D _(Mn),

-   -   wherein:        -   N_(Mn): atomic concentration of Manganese contained in the            copper alloy layer,        -   D_(o): diffusion coefficient of oxygen atom in the copper            alloy layer, and        -   D_(Mn): diffusion coefficient of manganese in the copper            alloy layer.

In the second aspect of the present invention described above, the heattreatment is applied under the predetermined condition. Due to this heattreatment, a barrier layer is formed so as to surround aninterconnection body. The barrier layer is formed of an oxide layerincluding manganese. The barrier layer has a position where the atomicconcentration of manganese is maximized in their thickness direction ofthe barrier layer. Accordingly, it is possible to manufacture a copperinterconnection structure featuring an interconnection body with a lowelectrical resistivity and superior conductivity.

In accordance with a third aspect of the present invention, a method forforming a copper interconnection structure includes the steps of:

forming a copper alloy layer including manganese having an atomicconcentration of not less than 1.0 atom % and not more than 25 atom %over a main body with insulating properties;

-   -   forming an insulating layer over the copper alloy layer;    -   removing parts of the copper alloy layer and the insulating        layer such that an insulating portion stacked on a copper alloy        portion is formed over the main body, wherein the copper alloy        portion includes:        -   a top surface side facing the insulating portion,        -   a bottom surface side facing the main body, and        -   two open surface sides exposed to a surrounding atmosphere;            and    -   applying a heat treatment under a predetermined condition after        the removing step, wherein the predetermined condition includes:        -   a temperature of not less than 150° C. and not more than            450° C., and        -   oxygen partial pressure being adjusted to be less than an            atomic concentration of oxygen (N_(o)) in the copper alloy            layer according to:

N _(o) =N _(Mn) *D _(o) /D _(Mn),

-   -   wherein:        -   N_(Mn): atomic concentration of Manganese contained in the            copper alloy layer,        -   D_(o): diffusion coefficient of oxygen atom in the copper            alloy layer, and        -   D_(Mn): diffusion coefficient of manganese in the copper            alloy layer.

In the third aspect of the present invention described above, the heattreatment is applied under the predetermined condition. Due to this heattreatment, a barrier layer is formed on a top surface side and on twoopen surface sides of an interconnection body. The barrier layer isformed of an oxide layer including manganese. The barrier layer has aposition where the atomic concentration of manganese is maximized intheir thickness direction of the barrier layer. This means that such abarrier layer may be formed even in a manufacturing method whereinterconnection patterns are formed by photolithography process.Accordingly, it is possible to manufacture a copper interconnectionstructure providing an interconnection body with a low electricalresistivity and higher conductivity.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating various embodiments, are intended for the purposes ofillustration only and are not intended to necessarily limit the scope ofthe disclosure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a cross-sectional view of an embodiment of a copperinterconnection structure and a compositional view of its barrierlayers.

FIG. 2 illustrates a schematic diagram of a process for manufacturing ofan embodiment of a copper interconnection structure.

FIG. 3 illustrates a schematic diagram of an example of a process formanufacturing a copper interconnection structure.

FIG. 4 illustrates a compositional view of the copper interconnectionstructure shown in FIG. 3.

FIG. 5 illustrates a cross-sectional view of an alternative embodimentof a copper interconnection structure and a compositional view of itsbarrier layers.

FIG. 6 illustrates a schematic diagram of a process for manufacturing ofan alternative embodiment of a copper interconnection structure.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described hereinafter withreference to the accompanying drawings, in which preferred exemplaryembodiments of the invention are shown. The ensuing description is notintended to limit the scope, applicability or configuration of thedisclosure. Rather, the ensuing description of the preferred exemplaryembodiments will provide those skilled in the art with an enablingdescription for implementing preferred exemplary embodiments of thedisclosure. It should be noted that this invention may be embodied indifferent forms without departing from the spirit and scope of theinvention as set forth in the appended claims.

Embodiments of the present invention relates in general to copperinterconnections and their manufacturing process. It is specificallyrelates to a new generation of copper interconnections with aninterconnection body made of copper, surrounded by a barrier layer on anelectric insulating layer

Referring first to FIG. 1, an embodiment of a copper interconnectionstructure 1 with a compositional view of its barrier layer 7 is shown. Across-sectional view of the copper interconnection structure 1 and anatomic concentration of manganese in the barrier layer 7 are shown,respectively, in FIGS. 1( a) and 1(b). The copper interconnectionstructure 1 may include an interconnection body 8, a barrier layer 7 andan electric insulating layer 3. The interconnection body 8 is made ofcopper and its outer surface 81 is surrounded by the barrier layer 7.The barrier layer 7 is made of two portions: (1) a first barrier layer 7a and 2) a second barrier layer 7 b. Accordingly, the outer surface 81of the interconnection body 8 is also made of two portions: (1) a firstouter surface 81 a and 2) a second outer surface 81 b. Thus, the firstbarrier layer 7 a is formed between the electric insulating layer 3 andthe first outer surface 81 a, where the first outer surface 81 a is partof the interconnection body 8 that faces the electric insulating layer3. Further, the second barrier layer 7 b is formed on the second outersurface 81 b, where the second outer surface 81 b is part of theinterconnection body 8, which is not facing the electric insulatinglayer 3.

In this embodiment, each of the first and second barrier layers 7 a and7 b is formed from an oxide layer containing manganese (Mn). Further, asshown in FIG. 1( b), each of the barrier layers 7 a and 7 b has aposition where an atomic concentration of Mn is maximized in a thicknessdirection of the barrier layers 7 a and 7 b.

Therefore, in each of the first and second barrier layers 7 a and 7 b,manganese is surely converted into an oxide layer with electricalinsulation properties. In this way, the barrier layer 7 may prevent theatomic diffusion of copper, from the interconnection body 8 into theinsulating layer 3. In addition, the atomic diffusion of atoms composingthe insulating layer 3, e.g. silicon (Si), into the interconnection body8 can surely be prevented. Therefore, it is possible to manufacture aninterconnection body featuring a barrier layer with a higher barrierproperty, against the atomic diffusion, and also superior in electricalinsulating properties. In addition, it is also possible to provide acopper interconnection structure featuring an interconnection body witha lower electrical resistivity and higher conductivity.

Further, in this embodiment, an atomic concentration of oxygen in thesecond barrier layer 7 b is maximized in close proximity to the positionwhere the atomic concentration of manganese is maximized. In addition,the maximum atomic concentration of manganese in the second barrierlayer 7 b is greater than the atomic concentration of manganese in thefirst barrier layer 7 a. As it will be discussed further below indetail, the second barrier layer 7 b is formed on the upper surface ofthe interconnection body 8, which exposes to the atmosphere containingoxygen at the time the barrier layer 7 is formed. Thereby, it becomespossible to surely prevent the oxygen in the atmosphere from intrudinginto the interconnection body 8 by configuring the second barrier layer7 b as described above. Therefore, further improvement may be achievedby providing the interconnection body 8 with lower resistivity andsuperior conductivity.

According to embodiments of the present invention, manganese in thesecond barrier layer 7 b is symmetrically disturbed centering theposition where the atomic concentration of the manganese is maximized inthe thickness direction. In addition, oxygen in the second barrier layer7 b is also symmetrically distributed centering the position where theatomic concentration of oxygen is maximized in the thickness direction.Therefore, it is equally possible to prevent impurities from intrudinginto the interconnection body 8 from the surface 7 s of the secondbarrier layer 7 b. Additionally, it is also possible to prevent thebidirectional movement of copper from the interconnection body 8 intothe surface 7 s of the second barrier layer 7 b due to the selfdiffusion of copper. Thereby, it is possible to obtain a barrier layerwith superior barrier properties. In this way, it is possible to furthersurely provide a copper interconnection structure 1 with aninterconnection body 8 featuring a lower resistivity and higherconductivity.

Referring next to FIG. 2, a schematic diagram of a process formanufacturing of an embodiment of a copper interconnection structure 1is shown. The first half of the manufacturing process is depicted inFIG. 2( a). As shown in this figure, the manufacturing process forforming the copper interconnection structure 1 begins first withproviding an opening 4, with a groove shape, in the insulating layer 3.Then, a copper alloy layer 5 containing manganese is formed on an innersurface side of the opening 4. Subsequently, a buried copper 6 is formedover the copper alloy layer 5 so as to substantially filling the opening4.

The latter half of the manufacturing process is depicted in FIG. 2( b).The manufacturing process continues with applying a heat treatment tothe structure shown in FIG. 2( a). By applying this heat treatment undera predetermined condition, manganese in the copper alloy layer 5 isdiffused toward the inner surface side of the opening 4 and an uppersurface side 6s of the buried copper 6 so as to form the barrier layer 7as well as the interconnection body 8. Thereby, an oxide layercontaining manganese is formed on the inner surface side of the opening4, facing the insulating layer 3, and the open surface 6s side of theburied copper 6, which is not facing the insulating layer 3. On theother hand, the interconnection body 8 is formed by unifying a part ofthe copper alloy layer 5 with copper from the buried copper 6 such thatthe interconnection body 8 is surrounded by the barrier layer 7 and thecopper interconnection structure 1 is formed, as shown in FIG. 2( b).The predetermined condition in which the heat treatment is applied tothe structure shown in FIG. 1( a) will be discussed further below indetail.

The barrier layer 7 is formed from the copper alloy layer 5 containingmanganese. Manganese in the copper alloy layer 5 has a diffusioncoefficient equal or greater than the self diffusion coefficient ofcopper. In addition, manganese as a main additive element of the copperalloy layer 5 is oxidized easily compared to copper. The main additiveelement is an element which is contained at the maximum concentrationamong the elements added to the copper alloy layer 5.

In this embodiment, the copper alloy layer 5 contains manganese as themain additive element, and subordinate elements other than manganese mayalso be added to the copper alloy layer 5. It is also preferable thateach of the subordinate elements, contained in the copper alloy layer 5,has a diffusion coefficient equal or greater than the self diffusioncoefficient of copper and be oxidized easily compared to copper.Examples of favorable subordinate elements, added to the copper alloylayer 5, may include Zinc (Zn), germanium (Ge), strontium (Sr), silver(Ag), cadmium (Cd), indium (In), tin (Sn), barium (Ba), praseodymium(Pr), and neodymium (Nd).

The copper alloy layer 5 is formed by a sputtering method using an alloymaterial of manganese and copper (Cu—Mn alloy) as a target. For example,in this embodiment, the copper alloy layer 5 is deposited on theinsulating layer 3 by a high-frequency sputtering method using a Cu-Mnalloy target, which contains manganese in a concentration range of notless than 1.0 atom % and not more than 25.0 atom % in concentration.Other embodiments may use other deposition procedure for forming thecopper alloy layer 5. Examples of other deposition procedure may includea physical vapor deposition procedure, such as ion plating method orlaser ablation method, or chemical vapor deposition (CVD) procedure,such as an atomic layer deposition (ALD) method, or spin coat procedure.

The copper alloy layer 5 is deposited on a dense or porous surface ofthe electric insulating layer 3 (inner surface of the opening 4). Inthis embodiment, the dense or porous surface of the insulating layer 3may contain silicon (Si), such as silicon carbide oxide (SiOC), siliconnitride oxide (SiNO), silicon fluoride oxide (SiFO), silicon dioxide(SiO₂) and the like. In some embodiments, the dense or porous electricinsulating layer 3 is formed from an organic silicon compound, such ashydrogen silsesquioxane (HSQ) or methyl silsesquioxane (MSQ) (refer to“Semiconductor Device (2^(nd) edition)—Physics and Technology” by S. M.Sze P346-347 above). In other embodiments, the dense or porous surfaceof the electric insulating layer 3 is formed from an organic carbidehydride, such as polyarylen. In yet other embodiments, the dense orporous surface of the insulating layer 3 is formed form a highpermittivity metal oxide, such as tantalum oxide (Ta₂O₅: relativepermittivity=25) or titanium oxide (TiO₂: relative permittivity=40)(refer to “Semiconductor Device (2^(nd) edition)—Physics and Technology”by S. M. Sze P347 above), or hafnium oxide (HfO₂), zirconium oxide(ZrO₂) and the like.

In this embodiment, the electric insulating layer 3 may be configuredfrom a single SiO₂ insulating layer. Alternatively, other embodimentsmay use multilayer structure for the electric insulating layer 3. Theinsulating layer 3 with multilayer structure may have a first insulatinglayer such as silicon oxide carbide (SiOC) and a second insulatinglayer, formed over the first insulating layer, made from differentmaterials such as silicon nitride (Si₃N₄), or silicon carbide nitride(SiCN), or silicon carbide (SiC). Another example of the multilayerstructure may include the first insulating layer made from a porous HSQlayer or MSQ layer having a plurality of pores with the average porediameter of about 1 nm, and the second insulating layer formed fromtantalum oxide (Ta₂O₅) which is formed from the oxidation of tantalum(Ta).

In what follows the predetermined condition in which the heat treatmentis conducted will be discussed. The reason for heat treating the copperalloy layer 5 is to diffuse manganese toward a joint interface with theelectric insulating layer 3 and/or toward the upper surface 6s form theburied copper 6. Thereby, the barrier layer 7, which in fact consists ofan oxide layer containing manganese is formed in close proximity to thejoint interface with the electric insulating layer 3 and to the uppersurface 6s. The heat treatment for forming the barrier layer 7 ispreferably applied at a temperature where the atomic diffusion becomesdominant by: (1) the electric field generated between the insulatinglayer 3 and copper alloy layer 5, and/or (2) the electric fieldgenerated in close proximity to the upper surface 6s of the buriedcopper 6. The second electric field is resulted from the oxygen (oxygenion) containing in the applied atmosphere, which is absorbed on theupper surface 6s in a form of Mn ion (Mn²⁺ or Mn³⁺), in which thevalence of manganese is divalent or trivalent.

Preferable temperature range for applying the heat treatment pertainingto the present invention is not less than 150° C. and not more than 450°C. When the temperature is above 450° C., the thermal diffusion rapidlyand significantly occurs compared to the case of diffusion by electricalfield. In a common heat treatment with a high temperature where thethermal diffusion becomes dominant, the diffusion of manganese in thecopper alloy layer 5 toward the upper surface side 6 s and the innersurface of the opening 4 is promoted. In this way, the thickness of thebarrier layer 7 increases in proportion to a square root of heattreatment time (√{square root over ( )}t). A disadvantage of the abovecase is when the thermal diffusion of manganese is further progressedafter the completion of the heat treatment. In this case, the thicknessof the barrier layer 7, which increases in proportion to the square rootof heat treatment time (√{square root over ( )}t), will increase furthersuch that it will exceed a desired range and result in forming anunstable barrier layer 7.

Meanwhile, when the temperature is at or below 450° C., the atomicdiffusion of manganese is dominated by electric field. In this case, thethickness of the barrier layer 7 slightly increases, which isproportional to the logarithmic values of heat treatment time (log(t)).For this reason, even though the barrier layer 7 is exposed to aresidual heat after the completion of the heat treatment, the thicknessof the barrier layer 7 will not increase rapidly. Therefore,temperatures at or below 450° C. are more favorable for forming anextremely thin barrier layer 7 in the copper interconnection structure 1with a narrow interconnection width, e.g., 32 nm or less.

In order to efficiently diffuse manganese in the copper alloy layer 5,it is preferable that the heat treatment to be applied in an atmospherecontaining oxygen with a favorable partial pressure. The favorablepartial pressure of oxygen is adjusted to be less than an atomicconcentration of oxygen No (atom %) in the copper alloy layer 5. Theatomic concentration of oxygen (No), which is in fact a dissolvedconcentration of oxygen, may be obtained according to the followingformula:

N _(o) =N _(Mn) *D _(o) /D _(Mn)

where N_(Mn) (atom %), Do (cm²/s), and D_(Mn) (cm²/s) representrespectively an atomic concentration of manganese, a diffusioncoefficient of oxygen, and a diffusion coefficient of manganese in thecopper alloy layer 5. Thus, it is necessary to heat-treat the copperalloy layer 5 in the atmosphere containing oxygen with the favorablepartial pressure, as described above. The atomic concentration ofmanganese (N_(Mn)) in the copper alloy layer 5 may be quantified, forexample, by a common secondary ion mass spectrometry (SIMS) method, anelectron probe micro analysis (EPMA) method, an Auger electronspectroscopy (AES) method and the like.

An example of calculating the favorable partial pressure of oxygen isgiven below. For an absolute heat treatment temperature T (K) and theuniversal gas constant R (R=8.3J/mol·K), the diffusion coefficient ofmanganese (D_(Mn)) may be given as follows:

D _(Mn)=1.02 exp(−200000/RT)   (1)

Further, the diffusion coefficient of oxygen (Do) may be given accordingto the following formula:

Do=1.20×10⁻² exp(−67000/RT)   (2)

Further, the solubility of oxygen (N_(sol)) in the copper alloy layer 5is proportional to the oxygen partial pressure (P₀₂) in the heattreatment atmosphere according to the following formula:

N _(sol)=26(P ₀₂)^(1/2) exp(−126000/RT)   (3)

Therefore, the oxygen partial pressure (P₀₂) can be obtained bycalculating the ratio value Do/D_(Mn) using the formula (1) and formula(2), and substituting N_(sol), which is obtained by multiplying theratio value by N_(Mn), in the formula (3). The favorable oxygen partialpressure pertaining to the present invention is the oxygen partialpressure less than the value calculated from the formula (3). This valueat a temperature of about 350° C. is 1.0 Pascal (Pa). More specifically,the most favorable oxygen partial pressure is ranging from 0.0001 to 0.1Pascal. Other embodiments may use some constituent atmosphere, such asvacuum or an inert gas, where the constituent atmosphere does not reactwith copper (Cu).

Examples of the inert gas atmosphere which does not react with Cu mayinclude nitrogen (N), argon (Ar), helium (He), neon (Ne), argon (Ar),krypton (Kr), xenon (Xe) and the like. Among the above inert gasatmospheres, helium (He), neon (Ne), or argon (Ar) are preferable. Inparticular, argon (Ar) with large molecules, which is difficult to betaken into the copper alloy layer 5, is more preferable.

When the copper alloy layer 5 is heat treated in the atmospherecontaining oxygen with the favorable partial pressure, the solubility ofoxygen N_(sol) exceeds the following value: N_(Mn)*Do/D_(Mn), thereby alarge amount of oxygen can be dissolved into the copper alloy layer 5,which poses a problem for forming the interconnection body 8 with a lowresistivity. Further, an upper surface 7 s of the second barrier layer7(b), becomes rough and not flat, thereby causing an inconvenience inthe passivation of the upper surface 7 s.

With reference to FIGS. 3-4, a practical example of the first embodimentpertaining to the present invention will be explained in detail. By wayof example, a copper interconnection structure 100 with a damascenestructure is explained. In this embodiment, the copper interconnectionstructure 100 is provided with a barrier layer 70, which is formed froma copper alloy layer 50 containing manganese as an alloy element.

A schematic diagram of an example of a process for manufacturing acopper interconnection 100 is shown in FIG. 3. The first half of themanufacturing process is depicted in FIG. 3( a). As schematically shownin this figure, a Cu—Mn alloy layer 50 (copper alloy layer) is firstdeposited on the inner surface side of the interconnection groove(opening) 40, which is formed on the insulating layer 30. In thisembodiment, the insulating layer 30 is made of silicon dioxide (SiO₂)layer with a thickness of 150 nm. The horizontal width of theinterconnection groove, or opening 40, is made to be about 50 nm. TheCu—Mn alloy layer 50 is formed by simultaneously sputtering a targetmade of high-purity Cu and a target made of high-purity Mn in a commonhigh frequency sputtering device. The atomic concentration of Mn in theCu—Mn alloy layer 50 is quantified to be about 4 atom % by electronenergy-loss spectroscopy (EELS) method. The thickness of Cu—Mn alloylayer 50 is about 30 nm.

Next, copper is plated on the surface of the Cu—Mn alloy layer 50 by anelectrolytic plating method using the Cu—Mn alloy layer 50 above as aseed layer. Thereby, a buried copper 60 is formed such that theinterconnection groove 40 is substantially filled. Thereby, a structurebody consisting of the Cu—Mn alloy layer 50 and the buried copper 60 inthe interconnection groove 40 of the insulating layer 30 is formed.

Thereafter, the structure body of FIG. 3( a), is heat treated for a timeperiod about 30 minutes at a temperature of about 350° C. The heattreatment is applied in an argon (Ar) atmosphere (oxygen volumeconcentration is not more than 0.01 vol.ppm (oxygen partial pressure0.001 Pa)) at a pressure of 1 atmosphere (0.1 mega-pascal (MPa) of totalpressure).

The oxygen volume concentration of 0.01 vol.ppm is determined asfollows: the diffusion coefficient of Mn (D_(Mn)) at a temperature ofabout 350° C. is calculated from formula (1): D_(Mn)=1.7×10⁻¹⁷ cm² s⁻¹.Then, the diffusion coefficient of oxygen (Do) at temperature of about350° C. is calculated from formula (2): Do=4.1×10⁻⁸ cm² s⁻¹.Furthermore, since the atomic concentration of Mn (N_(Mn)) in the Cu—Mnalloy layer 50 is 4.0×10⁻², the solubility of oxygen (No) is calculatedfrom formula (3) above: No=1.7×10⁻¹¹. Therefore, the oxygen partialpressure of the atmosphere is made to be 10⁻⁶ atmosphere pressure (0.1Pa), which gives the solubility of oxygen not more than 1.7×10⁻¹¹. Thatis, it is equal to 0.01 vol.ppm which sufficiently falls below 1vol.ppm, as an oxygen concentration when the total pressure isatmosphere pressure.

By this heat treatment, manganese contained in the Cu—Mn alloy layer 50is diffused toward the interface with the insulating layer (SiO₂) 30 andthe upper surface 60 s of the buried copper 60, which is open to theheat treatment atmosphere. Thereby the first barrier layer 70 a composedof manganese series oxide is formed between the insulating layer 30(SiO₂) and the interconnection body 80, as shown in FIG. 3( b). Further,the second barrier layer 70 b composed of Mn bearing oxide is formed incontact with the interconnection body 80 in the area proximity to theopening surface 60 s of the copper buried layer 60. The thickness of thefirst barrier layer 70 a is about 5 nm while the thickness of the secondbarrier layer 70 b is about 7 nm. Furthermore, the interconnection body80 is formed by unifying a part of the copper alloy layer 50 with thecopper from the buried copper 60 such that the interconnection body 80is surrounded by the barrier layer 70. In this way, the copperinterconnection 100 with damascene structure is formed.

After applying the heat treatment with the predetermined condition asdescribed above, the second barrier layer 70 b, the interconnection body80, the first barrier layer 70 a and the insulating layer 30 areexamined from the surface 70 s of the second barrier layer 70 b in avertical direction (depth direction) with a common electron energy-lossspectroscopy (EELS) method. Thereby, the concentration distribution ofthe elements in the above-mentioned layers is measured.

FIG. 4 illustrates a compositional view of the copper interconnectionstructure 100. In this figure, the distribution of atomic concentrationfor manganese (Mn), copper (Cu), and oxygen (O) is shown, respectively,in the second barrier layer 70 b, the interconnection body 80, the firstbarrier layer 70 a, and the interlayer insulating layer 30. The verticalaxis indicates the atomic concentration and the horizontal axisindicates the distance (depth) from the surface 70 s of the secondbarrier layer 70 b. As shown in FIG. 4, manganese (Mn) is locallyaccumulated inside of the first barrier layer 70 a and the secondbarrier layer 70 b. The atomic concentration of manganese is distributedin a normal distribution curve such that the maximum concentration islocated at the center of each of the barrier layers 70 a and 70 b. Inaddition, the atomic concentration of manganese is distributedsymmetrically centering around the position where the atomicconcentration of manganese is maximized.

The maximum atomic concentration of manganese in the second barrierlayer 70 b is greater than the atomic concentration of manganese in thefirst barrier layer 70 a. This maximum value in the second barrier layer70 b is about 1.45 times higher than the maximum value in the firstbarrier layer 70 a.

Further, in the second barrier layer 70 b, an atomic concentration ofoxygen (O) is maximized in close proximity to the position where theatomic concentration of manganese is maximized. Furthermore, oxygen inthe second barrier layer 70 b is symmetrically distributed centeringaround the position where the atomic concentration of oxygen ismaximized in the thickness direction. That is, similar to manganeseatom, the oxygen atom is showing a normal distribution curve, which issymmetrical at the center of the second barrier layer 70 b.

Since the heat treatment is performed in an atmosphere containing oxygenat the favorable partial pressure as described above, the open surface60 s of the copper buried layer 60 (surface 70 s of the second barrierlayer 70 b) is a flat surface without being rough. Further, the electricresistivity of the interconnection body 80 after the heat treatment isabout 1.9 μΩ·cm, which is virtually equal to pure copper (the electricresistivity for pure Cu bulk is 1.7 μΩ·cm). Therefore, it becomes clearthat embodiment of the present invention may provide copperinterconnections with low resistivity (close to a pure Cu bulkmaterial), which is favorable for manufacturing various electronicdevices.

Next, a second embodiment of the present invention in terms of copperinterconnection structure and its manufacturing process will beexplained with reference to FIGS. 5-6.

Referring next to FIG. 5, an alternative embodiment, the secondembodiment, of a copper interconnection structure 11 with acompositional view of its barrier layer 17 is shown. A cross-sectionalview of the copper interconnection structure 11 is illustrated in FIG.5( a). As shown in this figure, the copper interconnection 11 of thepresent invention may include an interconnection body 18, an electricinsulating layer 13 and a barrier layer 17. The interconnection body 18is formed between a main body 19 and the electric insulating layer 13.The interconnection body 18 is made of copper and its outer surface 181is surrounded by the barrier layer 17. The barrier layer 17 consists oftwo portions: 1) a first barrier layer 17 a and 2) a second barrierlayer 17 b. Accordingly, the outer surface 181 of the interconnectionbody 18 also consists of two portions: 1) a first outer surface 181 aand 2) a second outer surface 181 b. Thus, the first barrier layer 17 ais formed between the electric insulating layer 13 and the first outersurface 181 a, which is facing the electric insulating layer 13. Thefirst outer surface 181 a is positioned on the top surface of theinterconnection body 18. Further, the second barrier layer 17 b isformed on the second outer surface 181 b in proximity to open surfacesides of the interconnection body 18, which is not facing the electricinsulating layer 13.

Each of the first and the second barrier layers 17 a and 17 b iscomposed of an oxide layer having a position where the atomicconcentration of manganese is maximized in their thickness direction.

In this way, the distribution of atomic concentration of manganese inthe barrier layer 17 of the second embodiment is similar to thedistribution of atomic concentration of manganese in the barrier layer 7or 70 of the first embodiment of the present invention. Therefore,manganese is surely converted into an oxide layer with electricalinsulating properties in the first and the second barrier layers 17 aand 17 b. By these barrier layers, the atomic diffusion of copperforming the interconnection body 18 into the electric insulating layer13, and the atomic diffusion of atoms forming the insulating layer 13,such as silicon, into the interconnection body 18 may be surelyprevented. Therefore, it is possible to provide an interconnection bodywith a barrier layer, which is superior in barrier properties againstthe atomic diffusion and also superior in conductivity. Furthermore, itis also possible to provide a copper interconnection body with a lowelectric resistivity and superior conductivity.

In the second embodiment of the present invention, similar to the firstembodiment, the second barrier layer 17 b is formed in a way that theatomic concentration of oxygen is maximized in close proximity to theposition where the atomic concentration of manganese is maximized.Further, the maximum atomic concentration of manganese in the secondbarrier layer 17 b is greater than the atomic concentration of manganesein the first barrier layer 17 a. Since the second barrier layer 17 b isformed on the open surface sides of the interconnection body 18, whichare exposed to the atmosphere containing oxygen at the time of formingthe barrier layer 17, it becomes possible to surely prevent the oxygenin the atmosphere from intruding into the interconnection body 18. Thisprevention may be achieved by configuring the second barrier layer 17 bas described above. Therefore, it is possible to further improve thecopper interconnection structure 11 by providing an interconnection body18 with a lower resistivity and higher conductivity.

Furthermore, in the second embodiment of the present invention, similarto the first embodiment, manganese in the second barrier layer 17 b issymmetrically distributed centering the position where the atomicconcentration of manganese is maximized in the thickness direction. Inaddition, oxygen in the second barrier layer 17 b is also symmetricallydistributed centering the position where the atomic concentration ofoxygen is maximized in the thickness direction. Therefore, it is equallypossible to prevent impurities from intruding into the interconnectionbody 18 from the open surface sides 17 s of the second barrier layer 17b. Additionally, it is also possible to prevent the bidirectionalmovement of copper from the interconnection body 18 into the opensurface sides 17 s of the second barrier layer 17 b due to the selfdiffusion of copper. Thereby, it is possible to obtain a barrier layerwith superior barrier properties. In this way, it is also possible tofurther surely provide a copper interconnection structure 11 with aninterconnection body 18 featuring a low electric resistivity and higherconductivity.

FIG. 6 illustrates a schematic diagram of a process for manufacturing ofthe second embodiment of a copper interconnection structure. The firststep of the manufacturing process is shown in FIG. 6( a). As shown inthis figure, the manufacturing process for forming the copperinterconnection structure 11 begins first with depositing a copper alloylayer 15, made of copper-manganese (Cu—Mn) alloy, over a top surface ofthe main body 19. The main body 19 may include materials such assilicate glass with insulating properties. In the next step of themanufacturing process (FIG. 6( b)), the upper surface of the copperalloy layer 15 is covered with an electric insulating layer 13. FIG. 6(c) illustrates the third step of the manufacturing process. In thisstep, parts of the copper alloy layer 15 and the insulating layer 13 areremoved using some photolithography process and the like. This removingstep is performed in a way that an insulating portion 13 stacked on acopper alloy portion 15 is formed over the main body 19, leaving onlyareas where the copper interconnections will be formed. In thisembodiment, the copper alloy portion 15 may include a top surface sidefacing the insulating portion 13, a bottom surface side facing the mainbody 19, and two open surface sides 15 s directly exposed to asurrounding atmosphere. The last step of the manufacturing process isshown in FIG. 6( d). In this step, the structure body of FIG. 6( c) isheat treated under the same predetermined conditions as those describedin the first embodiment. By applying this heat treatment, manganese inthe copper alloy portion 15 is diffused toward the electric insulatingportion 13 and two open surface sides 15 s so as to form the barrierlayer 17 as well as the interconnection body 18. Thereby, an oxide layercontaining manganese is formed on the top surface side of the copperalloy portion 15, facing the electric insulating portion 13, and the twoopen surface sides 15 s of the copper alloy portion 15, which is notfacing the insulating portion 13. On the other hand, the interconnectionbody 18 is formed by transforming a part of copper alloy portion 15 intoa layer essentially made of copper and surrounded by the barrier layer17 and the main body 19. In this way, the copper interconnectionstructure 11 is formed as shown in FIG. 6( d). In the second embodiment,similar to the first embodiment, the electric resistivity of theinterconnection body 18 is 1.9 μΩ·cm, which is virtually equal to theresistivity of pure copper (the electric resistivity of pure Cu bulk is1.70 μΩ·cm). Therefore, the embodiments of the present invention mayprovide copper interconnections with low resistivity (close to a pure Cubulk material), favorable for manufacturing various electronic devices.

In both copper interconnection structures 1 and 11, pertainingrespectively to the first and second embodiment of the presentinvention, the outer surfaces 81 and 181 of the interconnection bodies 8(80) and 18 are surrounded by the barrier layers 7 (70) and 17.Therefore, bidirectional diffusions such as the atomic diffusion of thecomponent materials or impurities of the insulating layers 3 (30) and 13into the copper interconnection bodies 8 (80) and 18, and the diffusionof copper from the copper interconnection bodies 8 (80) and 18 into theinsulating layers 3 (30) and 13, may be prevented even if an insulatinglayer is further deposited on the top surface of the copperinterconnection 1 or on the open surface sides of the copperinterconnection 11. Consequently, it is possible to manufacturesemiconductor devices featuring a plurality of copper interconnectionshaving a low electric resistivity. Examples of such a semiconductordevices may include low-power-consumption liquid crystal display (LCD)devices, flat display panels (FDP) devices, organic electroluminescence(EL) devices, inorganic EL devices and the like.

Moreover, in both copper interconnection structures 1 and 11, thebarrier layers 7 (70) and 17 are composed of an oxide layer containingmanganese having a position where the atomic concentration of manganeseis maximized in the thickness direction of the barrier layers 7 (70) and17. Furthermore, in the second barrier layers 7 b (70 b) and 17 b, theatomic concentration of oxygen is also maximized in close proximity tothe position where the atomic concentration of manganese is maximized.Therefore, it is possible to provide semiconductor devices with a highelectro-migration resistance while featuring simultaneously a lowinterconnection resistance. Examples of those semiconductor devices mayinclude large-scale integrated (LSI) systems which require a nanointerconnection of the interconnection width of 32 nm or less. Becauseof their low interconnection resistance, the RC time constant, at thetime of communicating an electrical signal, is low. Thereby displaydevices, such as a large-size LCD with low RC delay, may be structured.Furthermore, semiconductor devices, such as silicon (Si) LSI whichrequires a damascene type fine interconnection, may also be favorablystructured.

Furthermore, in both embodiments, the outer surfaces 81 and 181 of theinterconnection bodies 8(80) and 18 are covered by the second barrierlayers 7 b (70 b) and 17 b. Thus, the second barrier layers 7 b (70 b)and 17 b may be formed without losing the smoothness and flatness of theouter surfaces 81 and 181 of the interconnection bodies 8 (80) and 18.Therefore, it is possible to manufacture semiconductor devices, such assilicon large-scale (LSI) systems, featuring multiple tandem copperinterconnection structures.

1. A copper interconnection structure comprising: an insulating layer;an interconnection body including copper; and a barrier layersurrounding the interconnection body, wherein the barrier layercomprises: a first barrier layer formed between a first portion of saidinterconnection body and the insulating layer, wherein the first portionof said interconnection body is part of the interconnection body thatfaces the insulating layer, and a second barrier layer formed on asecond portion of said interconnection body, wherein the second portionof said interconnection body is part of the interconnection body notfacing the insulating layer, and wherein: each of said first and saidsecond barrier layers is formed of an oxide layer including manganese,and each of said first and said second barrier layers has a positionwhere the atomic concentration of manganese is maximized in theirthickness direction of said first and said second barrier layers.
 2. Thecopper interconnection structure of claim 1, wherein the second barrierlayer comprises an atomic concentration of oxygen maximized in closeproximity to the position where the atomic concentration of manganese ismaximized.
 3. The copper interconnection structure of claim 1, whereinthe maximum atomic concentration of manganese in the second barrierlayer is greater than the atomic concentration of manganese in the firstbarrier layer.
 4. The copper interconnection structure of claim 1,wherein manganese in the second barrier layer is symmetricallydistributed centering around the position where the atomic concentrationof manganese is maximized in the thickness direction.
 5. The copperinterconnection structure of claim 2, wherein oxygen in the secondbarrier layer is symmetrically distributed centering around the positionwhere the atomic concentration of oxygen is maximized in the thicknessdirection.
 6. A method for forming a copper interconnection structure,the method comprising the steps of: forming an opening in an insulatinglayer, wherein the opening comprises an inner surface side facing theinsulating layer; forming a copper alloy layer including manganesehaving an atomic concentration of not less than 1.0 atom % and not morethan 25 atom % on the inner surface side; forming a buried copper overthe copper alloy layer so as to substantially filling the opening; andapplying a heat treatment under a predetermined condition after theburying step, wherein the predetermined condition includes: atemperature of not less than 150° C. and not more than 450° C., andoxygen partial pressure being adjusted to be less than an atomicconcentration of oxygen (N_(o)) in the copper alloy layer according to:N _(o) =N _(Mn) *D _(o) /D _(Mn), wherein: N_(Mn): atomic concentrationof Manganese contained in the copper alloy layer, D_(o): diffusioncoefficient of oxygen atom in the copper alloy layer, and D_(Mm):diffusion coefficient of manganese in the copper alloy layer.
 7. Themethod as recited in claim 6, wherein the step of applying the heattreatment comprises a step of diffusing manganese in the copper alloylayer toward the inner surface side of the opening and an upper surfaceside of the buried copper so as to form a barrier layer and aninterconnection body including copper.
 8. The method as recited in claim7, wherein the interconnection body is formed by unifying the buriedcopper with a part of the copper alloy layer such that theinterconnection body is surrounded by the barrier layer.
 9. The methodas recited in claim 7, wherein the barrier layer is formed of an oxidelayer including manganese and comprising: a first barrier layer formedbetween the insulating layer and an inner surface side of theinterconnection body, and a second barrier layer formed on an uppersurface side of the interconnection body.
 10. The method as recited inclaim 6, wherein the copper alloy layer is formed by a high-frequencysputtering deposition process, physical deposition process, or chemicalvapor deposition process.
 11. The method as recited in claim 6, whereinthe inner surface side comprises a dense or porous surface of theinsulating layer including silicon, an organic silicon compound, anorganic carbide hydride, or a high permittivity metal oxide.
 12. Themethod as recited in claim 6, wherein manganese in the copper alloylayer has a diffusion coefficient equal or greater than a self diffusioncoefficient of copper.
 13. The method as recited in claim 6, wherein thecopper alloy layer further comprises subordinate elements each having adiffusion coefficient equal or greater than the self diffusioncoefficient of copper.
 14. A method for forming a copper interconnectionstructure, the method comprising the steps of: forming a copper alloylayer including manganese having an atomic concentration of not lessthan 1.0 atom % and not more than 25 atom % over a main body withinsulating properties; forming an insulating layer over the copper alloylayer; removing parts of the copper alloy layer and the insulating layersuch that an insulating portion stacked on a copper alloy portion isformed over the main body, wherein said copper alloy portion comprises:a top surface side facing the insulating portion, a bottom surface sidefacing the main body, and two open surface sides exposed to asurrounding atmosphere; and applying a heat treatment under apredetermined condition after the removing step, wherein thepredetermined condition includes: a temperature of not less than 150° C.and not more than 450° C., and oxygen partial pressure being adjusted tobe less than an atomic concentration of oxygen (N_(o)) in the copperalloy layer according to:N _(o) =N _(Mn) *D _(o) /D _(Mn), wherein: N_(Mn): atomic concentrationof Manganese contained in the copper alloy layer, D_(o): diffusioncoefficient of oxygen atom in the copper alloy layer, and D_(Mn):diffusion coefficient of manganese in the copper alloy layer.
 15. Themethod as recited in claim 14, wherein the step of applying the heattreatment comprises a step of diffusing manganese in the copper alloyportion toward the top surface side and two open surface sides so as toform a barrier layer and the interconnection body including copper. 16.The method as recited in claim 15, wherein the interconnection body isformed by transforming a part of copper alloy portion into a layeressentially made of copper and surrounded by the barrier layer and themain body.
 17. The method as recited in claim 15, wherein the barrierlayer is formed of an oxide layer including manganese and comprising: afirst barrier layer formed between the insulating portion and a topsurface side of the interconnection body, and a second barrier layerformed on an open surface side of the interconnection body.
 18. Themethod as recited in claim 14, wherein the main body with insulatingproperties comprises silicate glass.
 19. The method as recited in claim14, wherein the copper alloy layer is formed by a high-frequencysputtering deposition process, physical deposition process, or chemicalvapor deposition process.
 20. The copper interconnection structure ofclaim 14, wherein manganese in the copper alloy layer has a diffusioncoefficient equal or greater than a self diffusion coefficient ofcopper.
 21. The copper interconnection structure of claim 14, whereinthe copper alloy layer further comprises subordinate elements eachhaving a diffusion coefficient equal or greater than the self diffusioncoefficient of copper.
 22. A semiconductor device having a copperinterconnection structure as a circuit interconnection, wherein saidcopper interconnection structure is the copper interconnection structurerecited in claim 1.